A conventional redundant power system usually consists of multiple sets of power supplies that share a common housing and a power integration back panel for control. In practice, it is called an N+M structure, where N is the number of power supplies to be clustered to meet total loading requirement of industrial computers, and M is the number of the power supplies allowed to be disabled. Taking 2+1 structure as an example, it consists of three sets of power supplies. The 1 at the rear means that one power supply may be disabled while other power supplies can still provide regular power needed. Depending on different requirements, an N+2 structure may also be adopted.
R.O.C. patent publication No. 562163 entitled “Redundant power supply” has a housing 10 and more than one track room 14 inside to house more than one power supply 30 connecting to a plurality of connectors 12 on a circuit board 11. The circuit board 11 integrates output power of the power supply 30 to form a redundant power.
The circuit board 11 previously discussed is the “back panel” commonly called in the redundant power supply. The main function of the back panel is to integrate the power of multiple power supplies and to also transform the power to supply output power at more than one different potential. With meeting the prevailing trend of demanding slim and light, the redundant power system also has to be made compact. Hence, the individual power supplies have to be made smaller, and the back panel also has to be shrunk. Such demands create problems in practice, notably:
First, to shrink the circuit board is difficult. As the back panel provides two basic functions of power integration and transformation, significant amount of power and current are converged on the back panel. Hence, a sufficient insulation capability has to be provided to meet safety regulations. Decreasing the size generally reduces the insulation capability. And voltage-resistance and insulation specifications of circuit elements also have to be enhanced. All this makes design more difficult and cost higher.
Second, heat radiation also is more difficult. Given the same amount of current and power integration and transformation, heat radiation on the smaller back panel is more difficult. Moreover, the dimensions of electronic elements for a greater current also are larger and cause the radiation space for airflow smaller. The smaller back panel has a higher power density in a unit area and a smaller area in contact with the air, and results in poorer heat radiant elements. As a result, malfunction probability increases.
Third, the power converged from all the power supplies are transformed to voltages of 12V, 5V or 3.3V or other potentials according to loading requirements. The conventional back panel has a transformed power and voltages set for the transformation circuit during design. Hence, alteration of the power and voltages is difficult to meet different loading requirements. This also limits the expandability of the redundant power system. For instance, even if the power supplies at the front end of the redundant power system are expandable, the back panel at the rear end has a fixed number of output lines and voltages, thus expandability is constrained.